Bi-directional propulsion caster

ABSTRACT

A bidirectional propulsion caster assembly is disclosed for enabling a rider to generate bi-directional motion from a ride-on device. A mounting bracket is attachable to the bottom of the device and defines a pivot axis extending in a generally transverse direction across the bottom of the device. A rocker bracket and caster shaft having a caster shaft axis are attached to the mounting bracket and pivot about the pivot axis along an arc between first and second positions. A wheel bracket is mounted to and rotates about the caster shaft. A wheel is mounted to the wheel bracket for rotation about a wheel axis angularly offset from the caster shaft axis. One or more changeable pivot stops may be attached to the rocker bracket or the mounting bracket and effective to further define the available arc of rotation.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/433,568, filed Apr. 30, 2009, which claims the benefit of U.S.Provisional Application No. 61/049,125, filed Apr. 30, 2008.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

REFERENCE TO SEQUENCE LISTING OR COMPUTER PROGRAM LISTING APPENDIX

Not Applicable

BACKGROUND OF THE INVENTION

The present invention relates generally to caster assemblies. Moreparticularly, in various embodiments, the present invention relates tocaster assemblies for use with ride-on devices. Even more specifically,this invention, in particular embodiments, pertains to an adjustablerocking action caster assembly for improved performance of recreationalskateboards, caster boards, and the like.

There are numerous ride-on devices in the marketplace. Ride-on devicestake many forms and may be used for exercise, entertainment or both.They may have a non-descript, mostly functional aesthetic form, like askateboard or scooter, or they may be made to look like a vehicle, ananimal or, a fictional character as with many preschool toys.

Conventional skateboards are generally supported by two-wheeled truckassemblies attached to the undersides of the boards. Such skateboardshave long been popular, but are limited in the sense that the ridercould realistically accelerate on a level or uphill surface only byremoving one of his or her feet from the board and pushing off theground. Typically such skateboards were also limited in the degree ofsteering that was possible, as where the turning radius reached acertain angle, the wheels would touch the board.

There is a desire and need in the marketplace for ride-on products thatcan be propelled in a way that is more novel than simply pushing off,and that may provide sharper turns if desired.

Caster boards were subsequently developed to address the limitations ofskate boards. U.S. Pat. No. 7,195,259 provides certain examples ofcaster, boards. Caster boards typically have comprised one or twoboards, with at least one swivel caster wheel assembly in front and atleast one in the rear of the caster board. The rider twists his or herbody to the left and to the right to accelerate the caster board or toturn it within a relatively small turning radius. This is accomplishedby having the wheels rotate around the wheel axis when the board istwisted in either direction, where the wheel axis is mounted at an acuteangle with respect to the bottom, front and back of the caster board.

In these prior art caster boards, the distance from the bottom side ofthe board to the contact point of the wheel to the riding surfaceincreases as the wheel bracket rotates around the axis in eitherdirection from its lowest forward facing position until the distancereaches maximum when the wheel bracket is rotated 180 degrees from itsneutral position. Propulsion is a resultant force causing the wheels tomove along the riding surface according to their bias as a rider appliesa force to twist the board and cause the casters to rotate around theaxis. In common caster boards this action will produce propulsion in thegeneral direction opposite of the acute angle formed by the wheel axisto the board. These prior art caster boards have a defined front and adefined back. The front and back are defined by the acute angle of thewheel axis. When the wheel bracket is rotated 180 degrees around theaxis, the distance between the bottom side of the board and the pointwhere the wheel contacts the riding surface is at its maximum. Becausethere is no force to bias the wheels against, propulsion in thisdirection is not possible. Therefore, the prior art caster board has adefined front and back and are unidirectional with regard to propulsion.

In contrast, skateboards and the art of skateboarding have benefitted inregard to the tricks able to be performed and their subsequentpopularity by their ability to go either direction with equalcapability. Therefore it would be beneficial to the art if a casterboard could be bidirectional and travel in either direction with equalcapability.

Moreover, in common prior art caster boards, the angle of the wheel axiscannot be adjusted by the rider according to his skill level, chosenactivity or preference. In contrast, many sport type ride-on devices,such as BMX bicycles and common skateboards, retain the interest of theuser partly due to the fact they can be customized to affect performancevia changeable parts such as sprockets, trucks and other paraphernalia.

Typical prior art caster boards have a front and a back defined by itsability to propel itself in a general direction which is determined bythe acute angle at which the wheel axis is mounted. This design limitscaster boards to be unidirectional and leaves a desire in themarketplace unfulfilled.

Some ride-on devices have used a spring to work against the rotation ofthe wheel assembly along the wheel axis, thus creating a force thatreplaces the gravitational force used in other prior art devices. Thismethod still provides forward motion resulting from side-to-side, ortwisting, forces applied by the rider. However, this does not allow fullrotation of the wheel assembly which limits the maneuverability of theride-on device. Moreover, the spring has a set tension so performancevaries greatly with the weight of the rider.

It is desirable therefore to provide a caster assembly that permits fullrotation of the wheel for bi-directional propulsion. This improvedperformance may include sharper turns, bi-directional travel, anduser-adjustable components for various preferences and/or skill levelsas examples. Other needs and potential for benefit may be apparent topersons of skill in the art having studied this document.

BRIEF SUMMARY OF THE INVENTION

It is an object of some embodiments of this invention to provide acaster assembly for ride-on devices such as caster boards that uses arocking caster to permit bidirectional propulsion, improve performance,or both, for example, for riders of all sizes. Some embodiment may haveother objects or benefits, some of which may be apparent from thisdocument.

In accordance with some embodiments of the invention, a caster assemblyincludes a wheel bracket, a wheel attached to the wheel bracket, arocker/shaft assembly about which the wheel bracket is free to rotate, amounting bracket attached to the underside of a ride-on device andconnected to the rocker/shaft assembly, and one or more pivot stops todictate the limits of the rocker/shaft assembly movement, for example.In some embodiments, the wheel assembly is attached to a caster shaftwhich rocks on the bracket by pivotally attaching to the mountingbracket.

When forces applied by the rider cause the wheel bracket to rotate 90degrees about the shaft, the rocker becomes level allowing for dynamicspins and other tricks. When the rider applies forces which cause thewheel bracket(s) to rotate around the shaft more than 90 degrees, theentire caster assembly rocks on the pivot-bracket connection creating anew low point 180 degrees around the caster from the previous lowposition. This allows the board to have no discernable front or backwith regard to propulsion and performance. This is accomplished bymounting the caster so that it does not have a constant acute angle inrespect to any given point on the bottom side of the board.

The rocking action of the assembly positions the caster to accelerate ineither direction by rocking when the wheel bracket rotates more than 90degrees from the low point on its rotation to create a new low pointwithin 90 degrees. Therefore, the wheel bracket never travels 180degrees from the low point where propulsion is no longer possible aswith conventional caster boards.

Thus, mounting the shaft or axis so it can swing its angle from acute toobtuse relative to a vector from one end of the board to beneath theshaft, rather than mounting the shaft at an acute angle with regard to afront and a back, creates a caster board with no front and no back thatcan go either direction with equal capability.

The rocker/shaft assembly of the present; invention can be designed tointerface with the bottom side of the board or the bracket so that theswing could be restricted to the desired amount. In some embodiments, aseparate piece such as a pivot stop can be introduced to dictate thewhere and how of this interface. The where could be dictated by theshape of pivot stop and the how can be dictated by the choice ofmaterials. In some embodiments, the pivot stops may be made fromurethane or other material that has rebound qualities.

Moreover, using a separate part allows the option to change this part tomodify the total swing angle and therefore the performance of thedevice.

Through the use of various embodiments of the invention, forward motionmay be easier to maintain than it is to initiate. Further, in a numberof embodiments, the caster assembly further permits the rider to travelbackwards as well as forwards. In different embodiments, the pivot stopsmay comprise a wide variety of configurations and some embodiments maybe easily changeable by the rider to accommodate various userpreferences and skill levels.

In accordance with other embodiments of the caster assembly, therocker/shaft assembly may interface directly with the bottom side of theride-on device or the main bracket to restrict the swing of therocker/shaft assembly. Also the main bracket may attach to therocker/shaft assembly with one or more pivot bolts or pins but in everycase it will be a common axis between these pins/bolts.

While many ride-on devices as contemplated by this invention may requiremore than one wheel to operate, only one propulsion caster assembly asdescribed may be required. However, the various caster assemblies of thepresent invention may be used in a variety of combinations with avariety of ride-on devices in some embodiments. The caster assembly may,in addition, comprise a blade instead of a wheel where the ride-ondevice is to be used on ice. Further, the caster assembly mayconceivably be used with devices that are not intended to be ridden suchas carts or wagons, as examples.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an embodiment of a ride-on device havingbi-directional propulsion caster assemblies attached.

FIG. 2A is an isometric view of an embodiment of the caster assembly ofthe invention.

FIG. 2B is an exploded isometric view of the caster assembly of FIG. 2A.

FIG. 3 is an exploded side view of the caster shaft of FIG. 2Ademonstrating the permissible arc of rotation of the caster shaft.

FIG. 4A is an isometric view of another embodiment of the casterassembly of the invention.

FIG. 4B is an exploded isometric view of the caster assembly of FIG. 4A.

FIG. 5A is an isometric view of another embodiment of the casterassembly of the invention.

FIG. 5B is an exploded isometric view of the caster assembly of FIG. 5A.

FIG. 6 is an isometric view of an alternative embodiment of a ride-ondevice having a caster assembly of the invention attached.

FIG. 7 is an isometric view of another alternative embodiment of aride-on device having a caster assembly of the invention attached.

DETAILED DESCRIPTION OF THE INVENTION

One embodiment of the invention is disclosed in FIG. 1. In thisembodiment, a bidirectional propulsion caster assembly 10 is presentedfor use with a ride-on device 12 having at least one base 14. Each base14 has a top side 16 for supporting the feet of a rider and a bottomside 18 to which the caster assembly 10 is attachable.

Referring now to FIGS. 2A and 2B, in the embodiment illustrated, thecaster assembly 10 includes a wheel 20 supported by a wheel bracket 22.The wheel 20 is attached so as to rotate freely along its entirecircumference. The wheel further rotates freely about a wheel axis 21.The wheel bracket 22 is rotatably connected to a caster shaft 24 havinga caster shaft axis 26 that is angularly offset from the wheel axis 21.In this embodiment the caster shaft 24 is connected to the wheel bracket22 using a wheel bracket bolt 28. The wheel 20 and the wheel bracket 22are free to rotate around the caster shaft 24 and about the caster shaftaxis 26. The benefits of the angularly offset wheel axis 21 from thecaster shaft axis 26 will be discussed below.

Still referring to FIGS. 2A and 2B, in the embodiment illustrated,mounting bracket 30 is attachable to the bottom side 18 of the base 14with caster shaft 24 pivotally connected to the mounting bracket 30. Inthis embodiment the pivotal connection includes a pivot assembly 32having a pivot pin 32 or bolt 32 connected to the mounting bracket 30using various fastening components as known in the art. The pivotassembly 32 in various embodiments may comprise bushings, washers,bearings, and the like such that the caster shaft 24 is adequatelypermitted to pivot about the pivot assembly 32. The mounting bracket 30and the pivot pin 32 further define a pivot axis 34 that extends in agenerally transverse direction across the bottom of ride-on device 12when the caster assembly 10 is attached to the ride-on device 12.

Referring now to FIG. 3, the caster shaft 24 is attached to the mountingbracket 30 so that the caster shaft 24 can pivot about the pivot axis 34along an arc 36 between a first position 38 and a second position 40. Inthis embodiment the mounting bracket 30 may be shaped such that thewheel assembly 22 or the caster shaft 24 engage the mounting bracket 30at either end of the arc 36, thereby defining the first position 38 andthe second position 40. In other embodiments, the wheel assembly 22 maybe shaped so as to engage the bottom side 18 of the base 14 at eitherend of the arc 36, or various alternative configurations that may beanticipated for defining the first position 38 and the second position40.

The caster shaft 24 and a laterally extending plane corresponding to thepivot axis of the caster shaft 24 together form an angle with respect toeither direction of movement for the ride-on device 12. The angle is notfixed at an acute angle with respect to any given direction of movement,but may instead be acute or Obtuse depending on whether the caster shaft24 is in the first position 38 or the second position 40. Pivoting ofthe caster shaft 24 between the first 38 and second position 40 furthercauses the caster shaft axis 26 to extend on opposing sides of an axisperpendicular in relation to a horizontal plane of the base 14 of theride-on device 12.

Referring now to FIGS. 4A and 4B, in an embodiment as illustrated arocker bracket 42 rather than the caster shaft 24 is pivotally attachedto the mounting bracket 30. The caster shaft 24 is attached to therocker bracket 42 that the caster shaft 24 and rocker bracket 42 aretogether able to pivot along the arc 36 between the first position 38and the second position 40 previously defined. In some embodiments, thecaster shaft 24 and rocker bracket 42 may be integrally formed from asingle material to define a single rocker/shaft assembly 44. In thisembodiment, the rocker bracket 42 or rocker/shaft assembly 44 may engagethe bottom side 18 of the base 14 when it pivots in either directionalong the defined arc, the engagement; thereby defining the firstposition 38 and the second position 40. In other embodiments the rockerbracket 42 or rocker/shaft assembly 44 as shown may engage the mountingbracket 30 when it pivots to the first or to the second position. Themounting bracket 30 in these embodiments may be shaped in any number ofconfigurations so as to selectably define the arc of rotation.

The pivotal connection in this embodiment is created by a pair of pivotbolts 32 engaging the rocker bracket 42 or rocker/shaft assembly 44 fromopposing sides of the mounting bracket 30. The mounting bracket 30 ismounted to the bottom side 18 of the base 14 with one or more mountingbracket bolts 54 and an equivalent number of mounting bracket nuts 52.Generally, the closer the pivot axis 34 is to the riding surface, thesmoother directional transitions will be.

One or more pivot stops 46 may be attached to the rocker bracket 42 orrocker/shaft assembly 44. The pivot stops 46 provide an interfacebetween the rocker bracket 42 or rocker/shaft assembly 44 and the bottomside 18 of the base 14 or the mounting bracket 30. The pivot stops 46further define the first position 38 and second position 40 by limitingthe scope of the arc of rotation permitted rocker bracket 42 orrocker/shaft assembly 44.

In different embodiments, the one or more pivot stops 46 may beimplemented in a wide variety of configurations. In some embodiments,the pivot stops 46 may further be formed of urethane or other equivalentmaterial having rebound qualities as known in the art. Some embodiments,the pivot stops 46 may be easily changeable by the rider or user toaccommodate various user preferences and skill levels. For example, therider or user may change pivot stops 46 so as to selectably increase ordecrease the scope of the arc of rotation. As used herein, “changeable”,when referring to a part such as the one or more pivot stops 46, meansthat the part can be removed and replaced without damaging the partusing the skill and tools ordinarily found in homes of most riders ofskateboards, caster boards, scooters, and the like.

Referring now to FIGS. 5A and 5B, in an embodiment as shown a pivot stop46 is attached directly to the mounting bracket 30 using mountingbracket bolts 54 and mounting bracket nuts 52, as well as interface nuts48 and interface washers 50. In other embodiments, alternative andequivalent fastening mechanisms as known in the art may be used as well.The rocker bracket 42 or rocker/shaft assembly 44 may be attached to themounting bracket 30 as previously described. In this embodiment therocker bracket 42 or rocker/shaft assembly 44 engages the pivot stop 46when it pivots to either the first position or the second position. Theshape or configuration of the pivot stop 46 thereby defines thepermissible scope of the arc of rotation for the rocker bracket 42 orrocker/shaft assembly 44. In certain embodiments the pivot stop 46 maybe changeable by the rider or user so as to desirably increase ordecrease the permissible scope of the arc of rotation.

In certain embodiments the caster shaft 24, rocker bracket 42 and/orrocker/shaft assembly 44 may be allowed to travel around the pivotconnection approximately 30-60 degrees. For descriptive purposes,assigning an angle extending downward from the base 14 and toward theriding surface a value of 270 degrees, and with the base for exampleoriented parallel with the riding surface, the rocker/shaft assemblywould in these embodiments be allowed to travel freely between 15 and 30degrees on either side of 270 degrees depending on the desiredperformance.

If a 30 degree total swing is used on a ride-on device 12 such as acaster board 12, for example, the caster board 12 will be easier to turnand spin but will generate lower speed. It is similar to the lowest gearon a bicycle. It will generate less speed but there will also be lessresistance to rider motions. In contrast, if a total swing of 60 degreeswas used it would be similar to the highest speed on a bicycle. Therewould be more speed with less motion but there would be greaterresistance against that motion.

Referring generally now to FIGS. 1-5, operation of the embodimentsillustrated may be described. A bi-directional ride-on device 12 havingone or more caster assemblies 10 mounted to the undersides 18 of one ormore bases 14 or platforms 14 has a first end and a second endcorresponding to either direction of movement. When the wheel 20 andwheel bracket 22 of each caster assembly 10 are substantially alignedwith a direction of movement, the associated shaft 24 is pivoted to aposition corresponding to the direction of movement. Further, when thewheel bracket 22 and shaft 24 are so positioned, a minimum position orheight for the base 14 or platform 14 with respect to the riding surfaceis defined.

The wheel bracket 22 is rotated about the shaft 24 in response tolateral forces supplied to the base 14 or platform 14 by a rider or userof the ride-on device 12. As the wheel bracket 22 rotates away from asubstantial alignment with the direction of movement, and up to a ninetydegree angle relative to the direction of movement, the height of thebase increases with respect to the riding surface. Resultant energygenerally corresponding to a weight of the rider or user subsequently isstored in the caster assembly 10 and is released as the platform 14 isforced back to a minimum height with respect to the riding surface,creating propulsion of the ride-on device 12 in the direction ofmovement.

When the wheel 10 and wheel bracket 22 are aligned at a ninety degreeangle relative to the direction of movement, a maximum position orheight for the platform 14 with respect to the riding surface isdefined. The shaft 24, rocker bracket 42 or rocker/shaft assembly 44further pivots to an orientation substantially parallel with respect tothe riding surface. In this position the rider or user may have amaximum ability or freedom to achieve various maneuvers, dynamic spinsand other tricks, as resistance to lateral forces applied by the user isminimal and the ride-on device 12 is generally receptive to control.Correspondingly, in this position the speed or acceleration of theride-on device will be at a minimum as the energy remains stored untilthe wheel bracket 22 moves back toward substantial alignment with eitherdirection of movement.

When the wheel 20 and wheel bracket 22 are rotated more than a ninetydegree angle with respect to the direction of movement previouslydescribed, the ride-on device is functional to maneuver and acceleratein equivalent fashion in an opposing direction of movement. The shaft24, rocker bracket 42 or rocker/shaft assembly 44 pivots about thepermissible arc 36 of rotation from the initial position to the opposingposition on the arc. The wheel bracket 22 subsequently seeks tosubstantially align itself with the new direction of movement, wherein aminimum position or height of the platform 14 with respect to the ridingsurface is attained equivalent to the minimum position associated withthe previous direction of movement. Operation of the ride-on device 12in this direction of movement generally corresponds to the operation forthe previous direction as described.

As may be understood from the foregoing embodiments as described, thecaster assemblies 10 have a bidirectional quality in large part becausethere is no constant acute angle for the caster shaft 24 with respect toany given point on the bottom side 18 of the platform 14. Rotating therocker/shaft assembly 44 or caster shaft 24 toward the first positioncorresponds with operating the ride-on device 12 in a first directionand rotating the rocker/shaft assembly 44 or caster shaft 24 toward thesecond position corresponds with operating the ride-on device in asecond direction. The first direction of movement is associated with afirst position of the wheel bracket 22 in substantial alignment with thefirst direction of movement. The second direction of movement incontrast is associated with a second position of the wheel bracket 22 insubstantial alignment with the second direction of movement. The wheelbracket 22 forms an acute angle in each case with respect to a vectorcorresponding to the associated direction of movement and extendingalong the platform 14 to the attachment with the mounting bracket 30. Inthis manner the caster assembly 10 always seeks a minimum position forthe platform 14 with respect to the riding surface that corresponds tothe direction of movement.

In the particular embodiment of the invention specifically illustratedin FIG. 1, the bi-directional ride-on device 12 has two bases 14connected by a connecting element 56 and having at least one casterassembly 10 attached to the bottom side 18 of each base 14. In variousembodiments, bases 14 may be adapted to support a rider's feet. Forexample, bases 14 may be of sufficient strength to support a rider andmay be made of a material having a relatively high coefficient offriction with the sole of a typical shoe that may be worn when riding aride-on device 12 of the embodiment. The caster assembly 10 may alsowork with numerous other embodiments of ride-on devices 12.

FIG. 6 illustrates a bi-directional ride-on device 12 having a firstbase 14 a and a second base 146 aligned along an axis coincident witheither direction of movement. A connecting element 56 having elasticproperties is connected between the two bases 14 a, b. In thisembodiment, the first base 14 a is attached to a steering column 58having a wheel bracket 22 such that the wheel 20 is able to pivot aboutthe axis of the steering column 58. A bi-directional propulsion casterassembly 10 is attached to the underside 18 of the second base 14 b, inthe embodiment shown, and permits the rider to sustain motion in eitherdirection of the ride-on device 12 without taking his or her feet off ofthe bases 14 a, b.

FIG. 7 illustrates a bi-directional ride-on device 12 having a firstmember 15 and a second member 15 aligned along an axis generallytransverse to either direction of movement, each member 15 having a footplatform 60 to support a rider. In particular, one of skill in the artwill recognize that each foot platform 60 should have sufficient surfacearea and structural rigidity so as to support a rider's feet during useof the device 12. The members 15 are each attached to a bracket 66, inthis embodiment, the attachments being pins or hinges 64 that permit themembers 15 to pivot laterally in either direction while steering column58 remains at the same nearly-vertical angle. There is also a supportelement 62, in this embodiment, pivotably attached on one end to acentral portion of the first member 15 and on the other end to a centralportion of the second member 15. The bracket 66 also is attached to asteering column 58, in this embodiment, and a wheel 20 that is able torotate about the axis of the steering column 58. There are twobi-directional propulsion caster assemblies 10, in this embodiment, oneattached to the underside of each foot platform 60, to permit the riderto sustain a forward motion in the ride-on device 12 without taking hisor her feet off of the platforms 60.

A number of embodiments of the present invention have been presentedherein. However, while certain embodiments of ride-on devices ascontemplated by this invention may require more than one wheel tooperate, only one bi-directional propulsion caster assembly as describedmay be required. The invention may be used in the context of a devicethat is not ridden, such as a cart or wagon. In other embodiments, theinvention could provide for a caster assembly using blades for use onice rather than wheels.

Thus, although there have been described particular embodiments of thepresent invention of a new and useful bidirectional propulsion caster itis not intended that such references be construed as limitations uponthe scope of this invention except as set forth in the following claims.

1. A bi-directional ride-on apparatus for use by a rider on a ridingsurface, the apparatus comprising: a plurality of base members, theplurality of base members each having a bottom surface and a top surfaceadapted to support the feet of a rider; at least one connecting elementconnecting the base members; and at least one caster assembly mounted tothe bottom surface of at least one base member, the at least one casterassembly comprising: a mounting bracket attached to the bottom surface,the mounting bracket defining a single pivot axis that extends in agenerally transverse direction across the bottom surface; a caster shafthaving a caster shaft axis, the caster shaft attached to the mountingbracket along the pivot axis so that the caster shaft can pivot aboutthe pivot axis along an arc between a first position and a secondposition on opposing sides of an axis that is perpendicular to ahorizontal plane of the base member; a wheel bracket mounted to thecaster shaft such that the wheel bracket rotates about the caster shaftaxis; and a wheel mounted to the wheel bracket for rotation about awheel axis that is angularly offset from the caster shaft axis, whereinthe apparatus has only two wheels, and one wheel is in front of theother wheel relative to the direction of movement of the ride-onapparatus along the riding surface.
 2. The bi-directional ride-onapparatus of claim 1, wherein the connecting element has elasticproperties.
 3. The bi-directional ride-on apparatus of claim 1, whereinthe distance between the first position and the second position isapproximately 30-60 degrees.
 4. The bi-directional ride-on apparatus ofclaim 1, wherein the top surfaces are of a sufficient strength tosupport a rider and have a relatively high coefficient of friction withthe sole of a shoe.
 5. The bi-directional ride-on apparatus of claim 1,wherein the caster assembly permits the rider to sustain motion withouttaking the rider's feet off of the top surfaces.
 6. The bi-directionalride-on apparatus of claim 1, wherein the apparatus has two base membersand each base member has only one caster assembly.
 7. The bi-directionalride-on apparatus of claim 6, wherein when the wheel brackets rotatearound the caster shafts while the wheels are in contact with the ridingsurface, the base members are caused to rise and fall with respect tothe riding surface.
 8. The bi-directional ride-on apparatus of claim 1,wherein the caster shaft is attached to the mounting bracket along thepivot axis through a rocker bracket that is permitted to pivot along thearc.
 9. The bi-directional ride-on apparatus of claim 8, wherein one ormore changeable pivot stops are attached to the rocker bracket and areeffective to limit the scope of the arc.
 10. A method of operating abi-directional ride-on apparatus comprising: providing thebi-directional ride-on apparatus of claim 1; standing on the topsurfaces; moving the bi-directional ride-on apparatus in a direction ofmovement; and rotating the wheel bracket with respect to the castershaft by applying forces transverse to the direction of movement to thetop surfaces.
 11. A bi-directional ride-on apparatus for use by a rideron a riding surface, the apparatus comprising: a platform having abottom surface and a top surface adapted to support the feet of a rider;and at least one caster assembly mounted to the bottom surface of theplatform, the at least one caster assembly comprising: a mountingbracket attached to the bottom surface, the mounting bracket defining asingle pivot axis that extends in a generally transverse directionacross the bottom surface; a caster shaft having a caster shaft axis,the caster shaft attached to the mounting bracket along the pivot axisso that the caster shaft can pivot about the pivot axis along an arcbetween a first position and a second position on opposing sides of anaxis that is perpendicular to a horizontal plane of the bottom surfaceof the ride-on device; a wheel bracket mounted to the caster shaft suchthat the wheel bracket rotates about the caster shaft axis; and a wheelmounted to the wheel bracket for rotation about a wheel axis that isangularly offset from the caster shaft axis, wherein the apparatus hasonly two wheels, and one wheel is in front of the other wheel relativeto the direction of movement of the ride-on apparatus.
 12. Thebi-directional ride-on apparatus of claim 11, wherein the distancebetween the first position and the second position is approximately30-60 degrees.
 13. The bi-directional ride-on apparatus of claim 11,wherein the top surface is of a sufficient strength to support a riderand has a relatively high coefficient of friction with the sole of ashoe.
 14. The bi-directional ride-on apparatus of claim 11, wherein thecaster assembly permits the rider to sustain motion without taking therider's feet off of the top surface.
 15. The bi-directional ride-onapparatus of claim 11, wherein the apparatus has only two casterassemblies.
 16. The bi-directional ride-on apparatus of claim 15,wherein when the wheel brackets rotate around the caster shafts whilethe wheels are in contact with the riding surface, the platform iscaused to rise and fall with respect to the riding surface.
 17. Thebi-directional ride-on apparatus of claim 11, wherein the caster shaftis attached to the mounting bracket along the pivot axis through arocker bracket that is permitted to pivot along the arc.
 18. Thebi-directional ride-on apparatus of claim 17, wherein one or morechangeable pivot stops are attached to the rocker bracket and areeffective to limit the scope of the arc.
 19. A method of operating abi-directional ride-on apparatus comprising: providing thebi-directional ride-on apparatus of claim 11; standing on the platform;moving the bi-directional ride-on apparatus in a direction of movement;and rotating the wheel bracket with respect to the caster shaft byapplying forces transverse to the direction of movement to the platform.